The effects of metabolic inhibitors other than azide and dinitrofluorobenzene (DNFB) on the coupling of the Na and K pumps in frog skeletal muscle will be investigated. Both azide and DNFB hve been found to induce a ouabain-sensitive Na:Na exchange in skeletal muscle fibers. Azide has been shown to inhibit the K pump considerably and thus to partially uncouple the Na:K pump in muscle. The metabolic bases for these effects are unknown though intracellular ATP and ADP levels are probably involved. We propose to use a wider range of metabolic inhibitors in an attempt to biochemically localize the actions of inhibitors on the Na:K pump coupling ratio. Inhibitors of glycolysis such as iodoacetic acid and uncouplers of oxidative phosphorylation such as dinitrophenol will be used in the study. In addition, properties of the Na pump in Myxicola giant axons will be investigated. Myxicola giant axons will be microinjected with 22-Na and the effects of internal Na and external Na, K and Ca on the Na pump will be determined. The kinetics of pump activation by thse cations will be deduced from the data. Myxicola giant axons wll then be internally dialyzed to study the effects of internal ATP levels on the Na pump. BIBLIOGRAPHIC REFERENCES: Sjodin, R.A., and O.E. Ortiz. 1975. Resolution of potassium ion pump in muscle fibers using barium ion. J. Gen. Physiol, 66:269-286. Beauge, L.A., and R.A. Sjodin. 1976. An analysis of the influence of membrane potential and metabolic poisoning wth azide on the sodium pump in skeletal muscle. J. Physiol. (Lond.). in press.